To identify the activity of recombinant subtilisins (subtilisin BPN' and subtilisin Carlsberg), three different zymography methods, SDS-fibrin zymography (SDS-FZ), reverse fibrin zymography (RFZ), and isoelectric focusing-fibrin zymography (IEF-FZ), were used. The recombinant subtilisins BPN' and Carlsberg did not migrate into the electrophoretic field based on a Laetymili buffer system, instead forming a "binding mode" at the top part of the separating gels with the SDS-FZ and RFZ techniques. Yet, this problem was resolved when using IEF-FZ with a pH range from 3 to 10. In addition, all these methods enabled the activity of a recombinant pro-subtilisin DJ-4 to be detected without a refolding pathway.